Impact of the environment on otolith shape and fluctuation asymmetry of Sarpa salpa collected from Tunisian lagoons

This study focuses on otoliths shape and size analysis of Sarpa salpa, 204 samples were collected from two lagoons located in the north-east of Tunisia. The objectives were (1) to examine the intra-and inter -population variation in otolith size using length (Lo), width (Wo) and area (Ao) measurements and their shapes via Fourier Elliptical Analysis, (2) to evaluate the relationship between fluctuating asymmetry following otolith biometric parameters and shape and (3) the intra-and inter-population development of otolith size and shape between 2015 and 2020. The analyses of otolith biometric data from the samples of Ghar El Melh lagoon showed a significant difference & DLANGBRAC;symmetry & drangbrac; in length and perimeter. However, some asymmetry was detected in width and area especially in 2015. Those results were confirmed with the study of otolith shape between the right and left sides within the Ghar El Melh lagoon population in 2015 and 2020. Although in the Bizerte lagoon, having a well pronounced symmetry in four biometric parameters in 2015 and 2020, we detected a symmetry of shape in 2015 and an asymmetry in 2020. This allows us to conclude that the shape analysis is more informative and relevant than the biometric analysis. The suggested cause of the fluctuating asymmetry (FA) of otolith size and shape within and/or between the populations of the two lagoons was discussed in relation to the developmental instability induced by the environmental stress present in these stations.